Method for conversion of biomass to chemicals and fuels

Abstract

This invention provides a method for thermally converting volatile fatty acid (VFA) salts to ketones by mixing dry calcium salts of VFAs with hot heat transfer agent in an evacuated container, thereby causing thermal decomposition of the calcium salts of VFAs to form ketone-containing vapor and calcium carbonate; and separating the ketone-containing vapor from the calcium carbonate and heat transfer agent by condensing a mixture of ketones from the ketone-containing vapor. This invention also provides a process for conversion of VFA salts, produced by anaerobic fermentation of cellulosic biomass, into liquid fuels, volatile fatty acids, aldehydes, alcohols, and lactic acid.

We claim: 
     
       1. A process for recovering low-boiling acids from a concentrated solution of calcium salts of the acids comprising contacting a concentrated solution of calcium salt of low-boiling acids with a low-molecular-weight tertiary amine and carbon dioxide,   forming calcium carbonate precipitate and a liquid solution containing low-molecular-weight tertiary amine/acid complex,   washing the calcium carbonate precipitate with water to remove residual low-molecular-weight tertiary amine,   replacing the low-molecular weight tertiary amine in the amine/acid complex with a high-molecular weight tertiary amine by an exchange reaction, and   thermally breaking the high-molecular-weight tertiary amine/acid complex and allowing the nonvolatile high-molecular-weight tertiary amine to separate from the volatile low-boiling acid.   
     
     
       2. The process of claim 1, wherein low-molecular-weight tertiary amine is also used in an amine dewatering step used to produce the concentrated solution of calcium salt of low-boiling acids. 
     
     
       3. The process of claim 1, wherein the high-molecular-weight tertiary amine/acid complex is thermally broken in a reactive distillation column. 
     
     
       4. The process of claim 1, wherein water is removed using multiple-effect evaporation or distillation or both prior to thermally breaking the high-molecular-weight tertiary amine/acid complex. 
     
     
       5. The process of claim 1, wherein salt precipitate is separated from the high-molecular-weight tertiary amine, washed with a volatile solvent, and the salt precipitate is dried to remove volatile solvent, the recovered wash fluid being separated using distillation. 
     
     
       6. The process of claim 5, wherein the volatile solvent is a low-molecular-weight amine. 
     
     
       7. The process of claim 6, wherein the same low-molecular-weight amine is used in the amine dewatering system. 
     
     
       8. The process of claim 1, wherein the washed calcium carbonate precipitate is additionally dried to remove residual volatile low-molecular-weight tertiary amine.